Conversion of hydrocarbon oil



July 23, 1935.-

E. F. NELSON- 2,009,119

CONVERSION OF HYDROCARBON OIL Filed Dec. 12, 1932 Frattz'orza for Condenser it)? W Patented July 23, 1935 UNITED STATES- CONVERSION OF HYDROCARBON OIL Edwin F. Nelson, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111.,

corporation of Delaware Application December 12, 1932, Serial No. 646,819

4 Claims.

This invention refers to an improved process and apparatus for the conversion of natural or casinghead gasoline for the purpose of producing motor fuel of wider boiling range than the charg- 5 ing stock and of high anti-knock value.

Natural gasoline, which is the liquid petroleum product recovered by compression, absorption or other means from natural gas, is used primarily for blending with less volatile distillates to produce composite motor fuel. The usual resulting blended motor fuel does not have the even chain of boiling points and the high anti-knock value required for high motor fuel efficiency and with the rapid adoption of modern cracking processes producing high yields of premium motor fuel for modern high compression engines, the demand for natural gasoline as blending material is rapidly diminishing.

The present invention anticipates another use for natural gasoline, when its economic value as a blending fluid has become of minor importance, by providing an improved process and apparatus for the pyrolytic conversion of natural gasoline to produce a motor fuel of a wider boiling range and of high anti-knock value.

I have found that the methods of cracking employed by the best present day processes for the conversionof relatively low boiling oils, wherein the high boiling intermediate conversion products are returned to further conversion together with the charging stock, are not the most suitable for the conversion of natural gasoline. This method of operation as applied to the treatment of natural gasoline results in the productionof high yields of gas and high yields of intermediate gasoline fractions leaving the motor fuel product of the process deficient in high boiling fractions.

The present invention overcomes this difficulty by recovering the high boiling motorfuel fractions produced by once-through treatment of the charging stock instead of returning a highpercentage of such material as reflux condensate t0 the heating coil for further conversion. The present process is further improved over the usual cracking operation by returning the excess quantity of intermediate motor fuel fractions to further conversion together with the charging stock under conditions which effect their conversion into substantial quantities of lower and higher boiling motor fuel fractions.

A more specific embodiment of the present invention may comprise subjecting natural gasoline to conversion at elevated temperature and superatmospheric pressure, separating from the resulting vaporous conversion products the relatively low boiling and the relatively high boiling motor fuel fractions, returning a portion of the intermediate boiling motor fuel fractions also recovered by said fractionation to further conversion together with the natural gasoline charging stock to 5 produce additional yields of low boiling and high boiling fractions, and finally commingling said low boiling and high boiling motor fuel fractions as I the final motor fuel product of the system.

It is also within the scope of the present inven- 10 tion as an optional feature of the operation of the process, to return any intermediate conversion products boiling above the end boiling point of the desired motor fuel product and below the high coke forming residual conversion products of the 1 process to further conversion together with the charging stock and the intermediate motor fuel fractions.

The accompanying diagrammatic drawing illustrates one specific form of apparatus for carrying 20 out the present invention although it should be understood that many other specific forms of apparatus are suitable for the practice of the process of the present invention and that the invention is not limited by the specific form of apparatus illustrated.

Referring to the drawing, natural gasoline, which comprises the raw oil charging stock for the system, is supplied through line i and valve 2 to pump 3 from which it is fed through line t and valve 5"to heating coil 6, which is located in the furnace l of any suitable form and by means of which the oil is heated to the desired conversion temperature preferably at a substantially superatmospheric pressure. It will be understood that the charging stock may, when desired, be preheated in any well known manner, not illustrated in the drawing, prior to its introduction into the heating coil. e

The heated oil is discharged from the heating coil 6 through line 8 and valve 9 into reaction chamber III, which is also preferably maintained at a substantial superatmospheric pressure, and, although not illustrated in the drawing, it is preferably well insulated to prevent the excesl sive loss of heat by radiation so that continued conversion of the oil, and particularly its vaporous components, may be accomplished in this zone.

Both vaporous and. residual liquid conversion products are withdrawn from a lower portion of chamber l0 through line H and valve I2 and are introduced into fractionator I 3 which in the case illustrated, serves as both a fractionating and separating column. Any heavy residual liqits uid produced by the operation, unsuitable for further conversion with the charging stock, may be withdrawn from the lower portion of fractionating and separating column 03 through line it and valve B5 to cooling and storage or to any desired further treatment. Uncondensable gas and lower boiling motor fuel fractions produced by the operation are withdrawn as the vaporous stream from the upper portion of the fractionator through line it and Valve ll to be subjected to condensation and cooling in condenser l8, from which the resulting distillate and uncondensalole gas passes through line it and valve it to collection in receiver 2i. Uncondensable gas may be released from the receiver through line 22 and valve 23. The distillate collecting in receiver 2i may be removed through line it and valve 25. When desired, a portion of the distillate from receiver 2i may be recycled as a cooling and reflux medium to the upper portion of fractionator it, by well known means not shown in the drawing, for the purpose of regulating the vapor outlet temperature from the fractionator and controlling the end boiling point of said low boiling fraction. The high boiling motor fractions produced by the operation are withdrawn as a side stream from the fractionator from a suitable point, for example, throughline 2t and valve 2? to cooler 28, from which they are withdrawn through line 29 and valve 30 or through line as and valve 30' to be blended with the low boiling motor fuel fractions recovered as distillate in receiver 21!, the blended product forming the final motor fuel product of the system.

A portion of the intermediate motor fuel fractions, comprising that portion of the material boiling substantially above the initial boiling point and substantially below the end boiling point of the desired final motor fuel product which are produced in quantities in excess of those required for a motor f-uel product of even burning characteristics, is removed from a suitable intermediate point in the fractionator, for example through line 3i and valve 32 to pump 33, to be returned therefrom through line 36, valve 35 and line 6 to heating coil 6 for further conversion together with the charging stock.

When the operation produces any substantial quantity of material boiling above the end boiling point of the desired motor fuel product which may be subjected to further conversion in the heating coil for the production of substantial quantities of additional motor fuel fractions without'the excessive production of coke and gas, this material may, instead of being blended with the residual liquid withdrawn, as already described, through line Ml and valve it, be removed as a separate fraction from the fractionator, for example, through line 36 and valve 3i into line ti and thence to pump 33 to be returned to further conversion in heating coil ii through line 34, valve 35 and line l, together with the intermediate motor fuel fractions and the natural gasoline charging stock.

The conversion conditions most suitable for the production of maximum yields of motor fuel of the desired wide boiling range and of high antiknock value will vary for natural gasoline charging stocks of diiferent grades and characteristics but may range, for example, from 950 to 1100 F., or thereabouts with a superatmospheric pressure of from 500 to 1000 pounds or thereabouts per square inch. In a system such as above illustrated and described these conditions apply to the temperature and pressure employed at the 'pheric pressure of about aooaiie outlet from the heating coil while substantially the same or. somewhat reduced pressure may be employed in the reaction chamber. A substantially reduced pressure ranging from 100 pounds or thereabouts, per square inch, down to substantially atmospheric or when desired, superatmospheric pressure substantially equalized with that in the reaction chamber may be employed in the succeeding separating, fractionating, condensing and collecting portions of the system.

As an example of one specific operation of the process of the present invention utilizing as charging stock a natural gasoline containing about 40% of material boiling up to 140 ll, it is subjected in the heating coil to a temperature of about 1000 F., at a superatmospheric pressure of approximately 800 pounds per square inch and substantially the same pressure is maintained in the reaction chamber. The vaporizing, fractionating, condensing and collecting portions of the system are operated at a superatmos- 100 pounds per square inch. Low boiling motor fuel fractions removed as the overhead vaporous products from the fractionator comprise distillate boiling up to approfimately 220 F. The high boiling fractions of the motor fuel product separately withdrawn from the fractionator comprise materials boiling be tween approximately 220 and 400 F. The excess production of intermediate motor fuel fractions, boiling up to approximately 325 1+1, is returned to further conversion in the heating coil together with the charging stock and with another stream of intermediate fractions from the fractionator boiling between approximately 400 to 550 F. This operation may yield, per barrel of charging stock, about 7'7 of motor fuel with an end boiling point of approximately 400 F., and an antilmock value equivalent to an octane number of approximately 80. The additional products of the system are uncondensable gas, asmall quantity of residual oil and a negligible amount of coke.

I claim as my invention:

1. A process for treating casinghead gasoline to produce motor fuel of wider boiling range and high anti-knock value which comprises heating the gasoline to a temperature adequate to increase the anti-knock value thereof, fractionating the resultant vapors and separating therefrom a light gasoline fraction, a heavy gasoline fraction, and an intermediate gasoline fraction boiling between the light and heavy fractions, returning the intermediate fraction to the heating step for retreatment in admixture with an additional quantity of the casinghead gasoline, combining said light and heavy fractions and recovering the resultant blend as the product of the process.

2. A process for treating 'casinghead gasoline to produce motor fuel of wider boiling range and high anti-knock Value which comprises heating the gasoline to a. temperature adequate to. increase the anti-knock value thereof, fractionating the resultant vapors and separating the same into a reflux condensate composed of hydrocarbons heavier than gasoline, a light gasoline fraction, a heavy gasoline fraction, and an intermediate gasoline fraction boiling between the light and heavy fractions, returning the intermediate fraction and the reflux condensate to the heating step for retreatment in admixture with an additional quantity of the casinghead gasoline, combining said light and heavy fractions and recovering the resultant blend as the product of the process.

3. A process for treating casinghead gasoline to produce motor fuel of wider boilinz range and.

aooaiie high anti-knock value which comprises heating the gasoline to a temperature adequate to increase the anti-knock value thereof, fractionating the resultant vapors and separating therefrom a light fraction boiling up to about 220 R, an intermediate fraction boiling up, to about 325 F., and a heavy fraction having an end boiling point of about 400 F., returning the intermediate fraction to the heating step for retreatment in ad 10 mixture with an additional quantity of the casinghead gasoline, combining said light and heavy fractions and recovering theresmltant blend as the product of the process.

4. The process as defined in claim 3 further characterized in that a reflux condensate heavier than gasoline is also separated from said vapors during the fractionation step and returned to the 

